Problem: Subtract. $\dfrac{9}{4} - \dfrac{9}{8} = $
Solution: Before we can subtract our fractions, they need to have the same denominator. $\dfrac{9}{4}$ $\dfrac{9}{8}$ $\dfrac{9}{4}-\dfrac{9}{8}$ Let's look at the multiples of each denominator and see which multiples they have in common. Denominator Multiples ${4}$ $4, \underline{8}, 12$ $8}$ $\underline{8}, 16, 24$ The least common denominator is ${8}$. Let's use multiplication to make each fraction have a denominator of $8$. ${\dfrac{9}{4}}=\dfrac{{9} \times {2}}{{4} \times {2}} = {\dfrac{18}{8}}$ Now, we can subtract ${\dfrac{18}{8}} - \dfrac{9}{8}}$. $\dfrac{18}{8}$ $\dfrac{9}{8}$ $\dfrac{18}{8} - \dfrac{9}{8}$ $=\dfrac{{18}-9}}{8}$ $= \dfrac{9}{8}$ ${\dfrac{9}{4}} - \dfrac{9}{8}} = \dfrac{9}{8}$ We can also write $\dfrac{9}{8}$ as $1\dfrac{1}{8}$.